The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore.
(1) Field of the Invention
This invention relates to acoustic projectors for sonar use and more particularly to a mount for a plurality of acoustic projectors in an array.
(2) Description of the Prior Art
U.S. Pat. No. 6,438,242 to Howarth discloses a cymbal transducer that can be deployed in a flat panel. It is often desirable to deploy a large number of these transducers in a planar array in order to provide a thin acoustic projector having a high acoustic source level.
The cymbal transducer consists of two caps having a dome portion and an edge portion bonded to a piezoelectric disk and in electrical conduction with the disk. When an electric field is applied to the disk, it expands and contracts in its radial direction. This expansion and contraction of the disk causes the dome portion of the caps to flex up and down sending acoustic energy into the surrounding medium. Further details of the cymbal transducer can be found in U.S. Pat. No. 6,438,242 which is incorporated by reference herein.
In the prior art, encapsulation and nodal mounting have been used to mount the cymbal transducers in an array. In the encapsulation technique, an array of the cymbal transducers is encased in polyurethane. This creates a very thin projector; however, the polyurethane damps the flexural motion of the caps, lowering the acoustic output. In addition, the presence of the polyurethane material makes replacement or repair of individual cymbal transducers cost prohibitive.
In the nodal mounting technique, each of the cymbal transducers is clamped around its outside rim. Material is not required around the dome portion of the caps, and damping does not occur. A first attempt at nodal mounting used copper clad circuit boards. Top and bottom circuit boards were provided having holes drilled in them to accommodate the dome portions of the caps. The edge portions of the transducers were held between the top and bottom boards. Plastic spacers were used to maintain a uniform distance between the top and bottom circuit boards. Although the flexing of the dome portion was unhindered, this mounting technique damped the radial motion of the piezoelectric disks causing undesirable vibration modes and abnormal acoustic radiation responses.
Accordingly, an object of the invention is to mount cymbal transducers in an array.
Another object is to provide a mounting structure for cymbal transducers that is relatively thin.
Still another object is to mount cymbal transducers without interfering with acoustic radiation from the cymbal transducers.
Yet another object is to mount cymbal transducers without transmitting radial vibration of the transducers.
Accordingly, the invention provides a mount for acoustic transducers which has a resilient sheet with a plurality of mounting apertures therein. Each mounting aperture has an annular groove formed about the inside surface of the sheet to accommodate one of the acoustic transducers. A pair of rigid, acoustically transparent plates are mounted on each side of the resilient sheet. Each plate has a plurality of communication apertures in it which correspond to the mounting apertures of the resilient sheet. The acoustic transducers are inserted into the mounting aperture of the resilient sheet. The acoustically transparent plates provide structural support for the mount.